A thin and light monitoring lens and imaging method thereof

Abstract

The present invention relates to a thin and light monitoring lens and an imaging method thereof, wherein the lens is composed of a first lens, a second lens, a third lens, a fourth lens and a glass plate which are sequentially arranged along the incident direction of light, an aperture is arranged between the first lens and the second lens, the first lens is a meniscus negative lens, the second lens is a double convex positive lens, the third lens is a double convex positive lens, the fourth lens is a meniscus negative lens, the first lens, the third lens and the fourth lens are aspheric lenses and all adopt plastic lenses; the second lens is a glass lens. The thin and light monitoring lens of the present invention adopts a four-piece structure of glass-plastic hybrid, the system has a small size, light weight, stable imaging quality, and has a low temperature drift characteristic within the temperature range of ‑40~85℃. The plastic lens adopts a low refractive index material, which greatly reduces the difficulty of plastic aspheric processing, the entire lens processing cost is low, suitable for large-scale production, the surface design and material matching are reasonable, and the imaging quality is excellent.

Description

Technical Field

[0001] The invention relates to the field of lenses, and in particular to a light and thin monitoring lens and an imaging method thereof. Background Art

[0002] With the continuous improvement of my country's optical processing capabilities, the application of aspheric surfaces in security lenses has become more and more extensive, which has made a qualitative leap in the imaging quality of such lenses. However, the excessive application of complex aspheric surfaces will inevitably lead to a sharp increase in processing costs and difficulties. If it is not controlled, it will lead to a large amount of resource waste. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a thin and light monitoring lens and an imaging method thereof which has small size, light weight, low processing cost and stable imaging quality.

[0004] The present invention is implemented by the following scheme: a thin and light monitoring lens, the lens is composed of a first lens, a second lens, a third lens, a fourth lens and a glass plate which are arranged in sequence along the incident direction of light, an aperture is arranged between the first lens and the second lens, the first lens is a meniscus negative lens, the second lens is a double convex positive lens, the third lens is a double convex positive lens, the fourth lens is a meniscus negative lens, the first lens, the third lens and the fourth lens are aspherical lenses and all adopt plastic lenses; the second lens is a glass lens; the total optical length TTL of the optical system and the focal length f of the optical system satisfy the relationship: TTL / f≤5.05; the F number of the optical system ≤1.60; the half image height ImaH of the optical system and the focal length f of the optical system satisfy the relationship: ImaH / f≥0.83.

[0005] Furthermore, the focal length ƒ of the optical system, the focal length ƒ1 of the first lens, the focal length ƒ2 of the second lens, the focal length ƒ3 of the third lens, and the focal length ƒ4 of the fourth lens satisfy the following relationship: -2.5< ƒ1 / ƒ<-0.3, 1.5< ƒ2 / ƒ<2.5, 0.1< ƒ3 / ƒ<1.5, -2.0<ƒ4 / ƒ<-0.5.

[0006] Furthermore, the first lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the second lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the third lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the fourth lens satisfies the relationship: N d ≥1.5, V d ≤50.0; where N d is the refractive index, V d is the Abbe constant.

[0007] Furthermore, the front and rear mirror surfaces of the first lens are both aspherical surfaces with a thickness of 0.933 mm; the front mirror surface of the second lens has a curvature radius of 8.153 mm, a curvature radius of the rear mirror surface is -8.153 mm, and a thickness of 4.987 mm; the front and rear mirror surfaces of the third lens are both aspherical surfaces with a thickness of 2.580 mm; the front and rear mirror surfaces of the fourth lens are both aspherical surfaces with a thickness of 0.827 mm; and the glass plate has a thickness of 0.730 mm.

[0008] Furthermore, the air gap between the first lens and the second lens is 4.87 mm, the air gap between the second lens and the third lens is 1.466 mm, the air gap between the third lens and the fourth lens is 0.076 mm, the air gap between the fourth lens and the glass plate is 0.983 mm, and the air gap between the glass plate and the image plane is 3.625 mm.

[0009] Another technical solution of the present invention is an imaging method of the thin surveillance lens as described above, wherein light passes through the first lens, the second lens, the third lens, the fourth lens and the glass plate from front to back in sequence to form an image.

[0010] Compared with the prior art, the present invention has the following beneficial effects: the thin surveillance lens of the present invention adopts a glass-plastic hybrid four-piece structure, the system size is small, the weight is light, the imaging quality is stable, and it has a low temperature drift characteristic within the temperature range of -40~85℃. The plastic lens adopts a low refractive index material, which greatly reduces the difficulty of plastic aspheric processing, the entire lens processing cost is low, suitable for large-scale production, the surface design and material matching are reasonable, and the imaging quality is excellent.

[0011] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments and related drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of the optical structure of an embodiment of the present invention;

[0013] Figure 2 is an axial chromatic aberration diagram of a working band of an embodiment of the present invention;

[0014] Figure 3 is a vertical axis chromatic aberration diagram of a working band of an embodiment of the present invention;

[0015] Figure 4 is a field curvature distortion diagram of a working band of an embodiment of the present invention;

[0016] Explanation of the numbers in the figure: L1-first lens; L2-second lens; L3-third lens; L4-fourth lens; L5-glass plate; STO-aperture; IMA-imaging surface. DETAILED DESCRIPTION

[0017] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0018] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0019] like Figures 1 to 4 As shown, a thin and light monitoring lens is composed of a first lens, a second lens, a third lens, a fourth lens and a glass plate which are arranged in sequence along the incident direction of light. The first lens is a meniscus negative lens, the second lens is a double convex positive lens, the third lens is a double convex positive lens, and the fourth lens is a meniscus negative lens. The first lens, the third lens and the fourth lens are aspherical lenses and are all made of plastic lenses. The second lens is a glass lens, and an aperture is arranged between the first lens and the second lens.

[0020] In this embodiment, the focal length ƒ of the optical system, the focal length ƒ1 of the first lens, the focal length ƒ2 of the second lens, the focal length ƒ3 of the third lens, and the focal length ƒ4 of the fourth lens satisfy the following relationship: -2.5< ƒ1 / ƒ<-0.3, 1.5< ƒ2 / ƒ<2.5, 0.1< ƒ3 / ƒ<1.5, -2.0<ƒ4 / ƒ<-0.5.

[0021] In this embodiment, the first lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the second lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the third lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the fourth lens satisfies the relationship: N d ≥1.5, V d ≤50.0; where N d is the refractive index, V d is the Abbe constant.

[0022] In this embodiment, the total optical length TTL of the optical system and the focal length f of the optical system satisfy the relationship: TTL / f≤5.05; the F number of the optical system ≤1.60; the half image height ImaH of the optical system and the focal length f of the optical system satisfy the relationship: ImaH / f≥0.83.

[0023] In this embodiment, the front and rear mirror surfaces of the first lens are both aspherical surfaces with a thickness of 0.933 mm; the front mirror surface of the second lens has a curvature radius of 8.153 mm, the rear mirror surface has a curvature radius of -8.153 mm, and the thickness is 4.987 mm; the front and rear mirror surfaces of the third lens are both aspherical surfaces with a thickness of 2.580 mm; the front and rear mirror surfaces of the fourth lens are both aspherical surfaces with a thickness of 0.827 mm; and the glass plate has a thickness of 0.730 mm.

[0024] In this embodiment, the air gap between the first lens and the second lens is 4.87 mm, the air gap between the second lens and the third lens is 1.466 mm, the air gap between the third lens and the fourth lens is 0.076 mm, the air gap between the fourth lens and the glass plate is 0.983 mm, and the air gap between the glass plate and the image plane is 3.625 mm; the aperture is close to the outer edge of the front end of the second lens, and the distance between the aperture and the center of the front end of the second lens is 0.316 mm.

[0025] In this embodiment, the refractive index of the first lens is 1.535, and the Abbe constant is 55.711; the refractive index of the second lens is 1.517, and the Abbe constant is 64.199; the refractive index of the third lens is 1.535, and the Abbe constant is 55.711; the refractive index of the fourth lens is 1.636, and the Abbe constant is 23.972; the refractive index of the glass plate is 1.517, and the Abbe constant is 64.199.

[0026] In this embodiment, the central curvature radius of the front mirror surface of the first lens is 4.649 mm, and the central curvature radius of the rear mirror surface is 1.737 mm; the central curvature radius of the front mirror surface of the third lens is 4.226 mm, and the central curvature radius of the rear mirror surface is -3.108 mm; the central curvature radius of the front mirror surface of the fourth lens is -2.542 mm, and the central curvature radius of the rear mirror surface is -22.669 mm.

[0027] The aspheric curve equations of the first lens, the third lens and the fourth lens are as follows:

[0028]

[0029] Wherein, Z is the height of the aspheric surface from the vertex of the aspheric surface when the aspheric surface is at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface; k is the cone constant; All are high-order coefficients.

[0030] The aspheric coefficients of each aspheric lens are as follows:

[0031]

[0032] The technical indicators achieved by the optical system are as follows:

[0033] (1) Focal length: 4.0mm≤EFFL≤4.9mm; (2) Aperture F≤1.60; (3) Working band: visible light.

[0034] The present invention adopts a glass-plastic hybrid four-piece structure, with small system size, light weight, stable imaging quality, and low temperature drift characteristics within the temperature range of -40~85℃. The plastic lens adopts low refractive index materials, which greatly reduces the difficulty of plastic aspheric processing. The entire lens processing cost is low, suitable for large-scale production, and the surface design and material matching are reasonable, and the imaging quality is excellent.

[0035] An imaging method for the thin monitoring lens as described above, wherein light passes through a first lens, a second lens, a third lens, a fourth lens and a glass plate from front to back in sequence to form an image, and the light also passes through an aperture between the first lens and the second lens.

[0036] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

[0037] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by integrated molding using a casting process) (except when it is obviously impossible to use an integrated molding process).

[0038] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0039] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0040] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A thin and light surveillance lens, characterized in that; The lens is composed of a first lens, a second lens, a third lens, a fourth lens and a glass plate which are sequentially arranged along the incident direction of light, an aperture is arranged between the first lens and the second lens, the first lens is a meniscus negative lens, the second lens is a double convex positive lens, the third lens is a double convex positive lens, the fourth lens is a meniscus negative lens, the first lens, the third lens and the fourth lens are aspherical lenses and are all plastic lenses; the second lens is a glass lens; the total optical length TTL of the optical system and the focal length f of the optical system satisfy the relationship: TTL / f≤5.05; the F number of the optical system is ≤1.60; the half image height ImaH of the optical system and the focal length f of the optical system satisfy the relationship: ImaH / f≥0.83; the focal length ƒ of the optical system, the focal length ƒ1 of the first lens, the focal length ƒ2 of the second lens, the focal length ƒ3 of the third lens, and the focal length ƒ4 of the fourth lens satisfy the following relationship: -2.5< ƒ1 / ƒ<-0.3, 1.5< ƒ2 / ƒ<2.5, 0.1< ƒ3 / ƒ<1.5, -2.0<ƒ4 / ƒ<-0.5; the front and rear mirror surfaces of the first lens are both aspherical surfaces, with a thickness of 0.933 mm; the front mirror surface of the second lens has a curvature radius of 8.153 mm, the rear mirror surface has a curvature radius of -8.153 mm, and the thickness is 4.987 mm; the front and rear mirror surfaces of the third lens are both aspherical surfaces, with a thickness of 2.580 mm; the front and rear mirror surfaces of the fourth lens are both aspherical surfaces, with a thickness of 0.827 mm; the thickness of the glass plate is 0.730 mm; the air gap between the first lens and the second lens is 4.87 mm, the air gap between the second lens and the third lens is 1.466 mm, the air gap between the third lens and the fourth lens is 0.076 mm, the air gap between the fourth lens and the glass plate is 0.983 mm, and the air gap between the glass plate and the image plane is 3.625 mm.

2. The thin and light surveillance lens according to claim 1, characterized in that: The first lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the second lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the third lens satisfies the relationship: N d ≥1.5, V d ≥50.0; the fourth lens satisfies the relationship: N d ≥1.5, V d ≤50.0; where N d is the refractive index, V d is the Abbe constant.

3. An imaging method of a thin surveillance lens as claimed in claim 1, characterized in that: The light passes through the first lens, the second lens, the third lens, the fourth lens and the glass plate from front to back to form an image.

Images